Electrolytic capacitor



Patented Nov. 11, 1952 UNITED STATES PATENT GFFICE ELECTROLYTICCAPACITOE George l. Stinson, Indianapolis, Ind., assignor' to P. R.Mallory & Co., Inc., Indianapolis, Ind., a corporation of DelawareApplication August 27, 1949, Serial No. 112,803W

16' Claims. l,

This invention relates generallyy to electrolytic apparatus and hasspecific application to such apparatus including means and methods forproviding electrolytic cells operable overwide temperature ranges;

The operation of electrolytic cells or capacitors substantially dependsupon a lm which may be formed on the surface of a metal, such asaluminumvor tantalum, when immersed in a suitable electrolyte andsubjected to electrical current; which film possesses the property ofallowing current to'ow from an electrolyte to the electrode with littleopposition, but of strongly opposing current now from the electrode tothe electrolyte.

The film so formed on the anode material acts as the dielectric for thecapacitor and is capable ofwithstanding very considerable voltageswithout eruption, and with very inconsiderable current leakage. It isfound, however, that this dielectric lm is sensitive to heat and thatits behavior is greatly dependent thereupon with a direct relationbetween the sensitiveness of the film-to heat and the temperature towhich it is subjected in the course of its formation or of itspreparation, that is to say, the higher the temperature during formationor preparation of the film, the higher will be the temperature which thefilm can afterwards withstand without serious impairment of itsessential properties.

Heretofore, electrolytic capacitors using tantalum as their nlm forminganode have not been produced or constructed so as to operate beyond thetemperature limits considered normal for aluminum capacitors; i. e. 40C. to plus 95 C. under optimum conditions. This is so because, in linewith what has been stated above, for a tantalum anode to operate in acapacitor at high temperatures it isl paramount that it bepreelectro-formed at as high, and preferably `a higher,` temperaturethan the subsequent operating temperature of the capacitor. Thus, if thecapacitor is to operate at a temperature above 175 C. the anode must beformed at a temperature substantially greater than that temperature.This fact thus necessitated a novel forming process heretoforeunavailable but which is now provided by the present invention.

Moreover, in addition to the problem of film formingy the. anodeVattemperatures substantially near 200 C. a capacitor operating at thesehigh temperatures` must include a suitable cathode materialwhichisinsoluble inan electrolyte of the..desi1'ed concentration attemperatures up to 200 C.; which electrolyte utilized therein shouldhave a low' electrical resistance at 60 C; Further in the constructionof thecapacitor a gasket material is utilized which acts as an'electrical insulator that is non-reactive to thev electrolyte at thishigh temperature. The cell orca'pacitor is also constructed so that itwill hold the electrolyte under all desired conditions of temperatureand pressure.

By the present invention, therefore, there is provided a compact,self-contained electrolyte cell or capacitor, using a'novel tantalumanode which has undergone a` novel forming process whereby theelectroformation is'encompassed in high boiling point sulphuric acidsuch that the formation is'carried out above 100 C., in fact. totemperatures in excess of 175 C. or even to the boiling point ofconcentrated sulphuric acid. An electrolytic capacitor is thusconstructed includ` ing all the constructional components desired andwhich is capable of being operated continuously at a predetermineddesired voltage over an ambient temperature range from 60 C. to 200 C.The capacitor, further, is capable of withstanding alternate periods ofexposure even beyond these latter temperatures.

It is, therefore, an object of the present invention to provide aA novelelectrolytic capacitor adapted for use over widely iiuctuatingtemperaturev ranges including extremes of heat and cold.

Yet another` object ofthe present invention is to provideanovelelectrolytic capacitor having a tantalum fabricated anodeV adaptedyfor use over Widely fluctuating temperature ranges.'

Still another objectof the present invention is to provide a newA typeof electrolytic capacitor operatingover a widely varying range oftemperatures including extremes of heat and cold, and which is capableof withstanding these temperatures without losing its seal.

Still another object of the present invention is to provide anelectrolytic capacitor unit operating over a widely varying range oftemperatures, for example, 60 C. to 200 C., and wherein said capacitoris constructed to f overcome pressure variations caused by the expansionand contraction of the various components` thereof when the unit iscycled between thev aforesaid temperature ranges.

Still another object ofthe present inventionis to. provide in acapacitor operating over a wide variation of temperature ranges, acathode which is insoluble in an electrolyte contained therewithin attemperaturesup to 200 C.`

Still. another object .of the. present inventionis to provide anelectrolyte having a 10W electrical A3 resistance in a tantalumelectrolytic capacitor operating between temperatures of 60 C. and 200C.

A further object of the present invention is to provide an electrolyticcapacitor having a suitable container capable of holding an electrolyteunder extremes of temperature and pressure.

Still another object of the invention is to provide a tantalumelectrolytic capacitor operating over a widely varying range oftemperatures, including extremes of heat and cold, with said capacitorincluding a gasket fabricated of a material capable of acting as anelectrical insulator and which is non-reactive with the electrolytecontained within said capacitor at extremes of high temperature, forexample, 200 C.

Another object of the present invention is to provide an electrolyticcapacitor having a tantalum anode which has undergone a novelelectroformation process whereby said capacitor is enabled to operate athigh temperatures.

Still another object of the present invention is toprovide a novelelectroformation process for a tantalum anode in the manufacture of acapacitor capable of operating at high temperatures.

The invention, in another of its aspects, relates to novel features ofthe instrumentalities described herein for teaching the principal objectof the invention and to the novel principals employed in theinstrumentalities whether or not these features and principals may beused in the said object and/ or in the said eld.

Other objects of the invention and the nature thereof will becomeapparent from the following description considered in connection withthe accompanying figures of the drawing and wherein like referencecharacters describe elements of similar function therein and wherein thescope of the invention is determined rather from the dependent claims.

For illustrative purposes the invention will be described in connectionwith the accompanying drawing in which:

Figure 1 is a vertical cross section view of an embodiment of the noveltantalum electrolytic vcapacitor (taken along line I-I of Figure 2)capable of operating over wide ranges of temperature, said capacitorincluding means for overcoming variations in the component assembly ofthe capacitor caused by expansion and contraction of the variouselements included therewithin;

Figure 2 is a sectional plan view of the embodiment of the inventiondisclosed in Figure 1 and which is useful in showing the compact cellarrangement of the capacitor and illustrating means for providingelectrical contact with the anode assembly of the capacitor; Y

Figure 3 is a vertical sectionalized view of an embodiment of theinvention capable of operation over widely varying ranges of temperaturevand having crimped means for obtaining closure of the severalcomponents of the capacitor; and

Figure 4 is a vertical cross sectional view of the tantalum electrolyticcapacitor invention showing an embodiment providing crimped closuremeans used in the assembly of the capacitor cell wherein vpreventivecompensating means is used therewith to substantially withstand andovercome variations caused by the expansion and contraction of thevarious components of the capacitor during the operation thereof.

Generally speaking, the present invention provides an electrolyticcapacitor capable of operyating over a widely varying range oftemperature.

for example, -60 C. to 200 C. instead of the heretofore usual range oftemperatures of 40 C. to plus C. The capacitor comprises a compactself-contained electrolytic cell adapted to operate continuously at agiven voltage throughout the above wide range of temperatures andprovides means for withstanding alternate periods of exposure to thelowest and highest temperatures, respectively, without losing its seal.IThe cathode of the capacitor is constructed of silver and because ofthe compact arrangement of the cell it may be constructed as thecontainer thereof.

In the construction of the capacitor or cell, a novel electro-formationprocess is used for the porous tantalum anode so as to provide an anodehaving a nlm which may remain undamaged by excessive acid concentrationat high temperature and which exhibits low electrical leakagecharacteristics when operated at voltages of the order of 65 volts at200 C. temperature.

Referring now to the drawing, Figure 1 is a cross sectional view of anembodiment of the tantalum anode electrolytic cell of the inventionwherein reference numeral I0 generally indicates the entire capacitor orcell structure. Capacitor I0 includes a container or casing I I having acircular or wafer configuration and is adapted for containing theelectrolyte of the cell, hereinafter described as being sulphuric acid.Casing II is further adapted by the unique construction of the cell tofunction as an electrode thereof; namely the cathode. Because of thespecial wide temperature and pressure range demand-s made upon the cell,the casing is of heavy wall construction and fabricated of fine silvermetal.

Cell I0 includes as its second electrode, an anode assemblyrconsistingof cell top I3 made from a tantalum sheet Hi connected to a tantalumpellet l5 fabricated of pressed and sintered metallic tantalum powder.The cell is sealed against electrolytic leakage by means of a maingasket I6 which also'functions to electrically insulate the anodeassembly from its associated cathode. A second gasket I'I is used toelectrically insulate the anode assembly from the case when the assemblyis completed. A screw cap 30 i'lts on the cell case and when tightenedholds the components of the cell together to complete the seal. Further,a cap contact ring and lead |30 provides means for a soldered or weldedelectrical contact with the anode assembly.

In the construction of the electrolyte cell, as above stated, casing i!has a generally circular or wafer shape. Casing i I is constructed so asto further the desired aim of providing a capacitor capable of operatingover widely varying temperature ranges and of coping with pressuresdeveloped and inducted within the cell by these varying temperatures.Because of the high pressure involved due to the operation of the cellat temperatures which may be considerably above the boiling' point ofthe electrolyte used and also because of the pressure caused by theformation gas due to electrical leakage current, a heavy walled case isused. Casing l! comprises a base section 20 including a bottom .portion25 having an inside wall surface 22 and an outside wall surface 23. Acircumferential wall section 2Q is connected to bottom 2| and includesside wall segments 25 and 2S with segment 26 including an inside wall 35and being interconnected to a lip extension 2l adapted to form a seat orstop for interlocking cap 30 as hereinafter described. Segment 26 has anoutside surface 28 threaded or serrated so as to provide .-threads; orzteethfx29 adapted to .mate with: the .threads or teetlrinofcap .30.' Atthe top offsection =there=isformed an inwardly extend-` ingaplatformextensionacomprising a collar 32 vand aztongue` 33 .extending VtherefromsoA as'to cooperate with agasket IS l-inithe sealing ofthe electrolytic: cell under` the:r stress 50i. varying ranges. of temperatureandzpressures;

Sincethe electrolytic cell' is adapted to operate over; widely varying.ranges 'oi' temperature'V and since the cell must be extremely compactand self contained, casing: Ilis adapted forfuseas the cathode.aele`ctrode of the scell. Eurther, .the Ycath-y odeiis .fabricatedgofametal found .to `have .espef cial suitabilityzwittrtlre sulphuricacidlelectrolyte utilized. Thisgsulphnric; acidi."` electrolyte; has adensity .of approximately 1.285 'at room tempera-y ture: rihis:concentration isffoundtozzbeithe optimum .electrolytic concentrationwhich. works as a: compromise betweenLthe'concentration havingthenlowest'l freezing pointandthat which possesses-maximumconductivity.In addition, it is found that sulphuric acid has the lowest freezingpoint and .resistance `of 'many electrolytes tested and examined.A

Asstated. it is desiredthat the cathode material -.which acts as thecell. container be such that itremain insolublefin'thedesiredelectrolyte of a determi-ned concentration at Vter-iperatures upto 200 C. It isfoundthatalthough silver-is readily solubleinhotconcentrated Ysulphuric acid, it is .only mildly attacked lay-solutionscontaining sulphuric` acidat `the boilingpcint of the solution.Thusthe-cathode of the cell is fabricatedo silverwith' the container orcasing constructed as aline silver-cellcase. In addition, to the abovegreat advantage, silver also has the advantage of being readilyelectroplated at extremely lovvl current densities: This fac-t tends tolimit the corrosion and reduce the cathode polarization fora capacitoroperated with an applied alternate current ripple voltage.

The anodey structure ci celll l0? is an assembly consisting of afcelltop i3 madeffrom atantalum metal -sheet i4 and an=tantalum pellet@5l-made from pressed and sintered tantalum metallic powder'.rliesinteredpellet l5 rnay be spot welded or otherwise 'formed bysuitable connecting means 5I to the tantalum top. rrheentirefl assemblyforms the anode yoi-the `capacitor celland also acts as the topthereof.'y

Because of the widely varying temperature and pressure needs thecapacitor is constructed Awith aspecial electrofermed tantaliun` anode.It was discovered after great-experimentation with plain tantalum foil,and later Awith pellets made from pressed and sintered metallictantalum, that when the tantalunr anode was electroformed to the 120volts D. C., at temperatures of approximately 200 C.A in sulphuric-acidelectrolytes; the anode had novel electrical characteristics withrespect to capacitance, direct current vle'akage'and `equivalent seriesresistance throughout theA temperature range of C. to 200l C.

However;l the electroformation` process posed greatfdiiculties, for itwas found that the opti mum maximum formation temperature wasapproximatelyw 17 5 C. Further; it--wasl considered desirable tocompletethe formation of the anode at temperatures somewhatiin excess ofr200" C.

Since'thev formation process is-carried outin an open vessel ortank, itis seen from the previous discussion thatthe'sulphuricxacid electrolyteemployed must `be of :sufficient `concentration .to have afboilingappint:equa-1 to or.iny excess iof rthe Ina-Xie' mum-l temperature desired..vFor example, sulphuric acidil solution containingy'72% HzSOrhas has aboilingpoint oi approximately175 C.; and for 200 C., the concentrationis about '79% sulphuric acid.

Further, when formation of the anodes' was carried out at 190 C. in 75%sulp-huric acid, it was found almost impossible to age capacitors at 65volts per `cell at 200 C. to a leakage of less than .7 ma. It thus maybe concluded that the concentration of acid at 190 C. is suiiicientlyhighV to produce permanent damageito the oxide lm. Again, units formedat 1759 C. in 72% acid may be aged to 65 volts percell at 200 C.' to aleakage of less .thanp inapproximately 48.hours.

In the present novel method of makingv the..tan.1 ta-lumcell, theanodeslare formed to volts at 175 C. and assembled into units. Theindividu'alunits are'then aged at 200 C. with a maximum `leakage of 2ma. per cell during the early stages of the aging process and then at amaximum of l ma. per cell until the leakage has reached 0.5 ma. percell.

Theelectrolyte used in a completed cell con'- sists Aof 39% sulphuricacidwith a boiling point of approximately 108 C. When this electrolyteis heated to 200 C. in the cell, a vapor pressure oi nearly 290 lbs/sq.in is obtained. The cell is so constructed as towithstand this pressurefor long periods of time and in addition withstand increased pressuredue to gas formation produced by the leakage current during operation.Moreover, if the leakage current exceeds l to 2 ma. for long periods oftime duringaging andsubseduent use, the eiiective life in service may bematerially reduced. Again, leakage current during operation tends toincreasel the strength or effective thickness of the dielectric lm witha subsequent reduction in capacitance. It is, therefore, essential thatthe unit be aged and operated at the lowest electrical leakage possible.

In order to avoid a longperiod of aging at high temperature, the formingoperation is carriedV outin several steps. In the rst step, the anodesare formed in an open tank to 120 volts at a maximum temperature of C.in 60% sulphuric acid electrolyte. When formation is sumciently completeto insure minimum gas generation at the anode and cathode at thetemperature and voltage speciiied, the anode is then transferred to a40% sulphuric acid solution in a container which is made pressure tight.The formation is then carried out to 120 volts at graduallyincreasedtemperatures up to 200 C. or higher untila leakage of 0.5'ma.or less per anode at 65 volts is obtained.

BvX the above method, anodes are produced having'alrn undamaged byexcessive acid concentration at' high temperature and exhibiting lowelectrical leakage characteristics when operatediat volts and 200 C. Itis to be noted, that inthe-above description of the process whereleakage values are given, they refer to eight gram tantalum: pelletshaving a density of 135`g;/in3 and a' capacitance of approximately 50mfd. when formed to 120V. D. C;

The. anode assembly, comprising tantalum sheet l and pellet l5, isinsulated from the cathode wall structure of the cell by means of agasket I, whose cross section has a wavelike appearance.` Gasket I 6'obtrudes between the cathode and anode structures of the cell and tsbetween cap 30 on collar 32 and tongue 33 of"cathoderseotion' 26.- Thegasket is'fabricated from the cathode circuit of the capacitor.

of a material suitable from the standpoint of corrosion resistance andhigh temperature characteristics, for example, polytetra-uoroethylenepolymer.

Since the gasket material tends to ow under pressure, it is apt to loseits seal unless confined in such wise as to retard ow in at least oneportion of the seal. Therefore, the tantalum top, the gasket and top ofthe cell, it will be noted, have been constructed that when the unit issealed a portion of the gasket material will always be conned undersufcient pressure to maintain an effective seal.

Further, due to the unequal expansion and contraction of the componentsconfining the capacitor it is found that a cell which may not leakelectrolyte when maintained at high temperatures for long periods oftime and cooled only to room temperature, may leak when subjected tosuccessive periods of operation at temperatures from 60 C. and 200 C. Toprevent electrolyte leakage during such cycling a heavy spring washer i8is provided between the overlying screw cap 3S and underlying insulatingwasher or gasket I?, and a Contact ring and tab di) which makes contactwith the anode assembly of the capacitor.

As stated, the anode is pre-electroformed. In order to pre-electroformthe anode assembly a tantalum contact must be made with the tantalum topand anode assembly. This is accomplished by spot welding a tab oftantalum ribbon to the cell top. Since tantalum cannot be soldered toitself or to other metals, this tab used in the formation is'broken oiand a contact ring and tab dll is connected to the anode assembly andserves as the anode lead. It is held securely Yin place by the overlyingsteel springr washer i8, described above.

Further, since spring washer i8 in contact with screw cap 3G, ifotherwise not prevented, will make electrical contact with contact ringand tab which ring and cap are electrically a part of the anode circuit,an insulator in the form cf a mica washer il is provided to electricallyinsulate tab fi!) and the anode assembly For this purpose a mica washerhaving high cornpression and high electrical breakdown strength is used.

When the capacitor is continuously operated over long periods or" timeat high temperatures, the high pressure developed thereby causes acontinuous escape of vapor from the cell. Since the tight constructionof the cell at 200 C. is such as to prevent loss of electrolyte, therewill only be a weight loss of approximately .05 to 0.1 milligram perhour. This loss, although insuiicient to aiect the operation of thecapacitor, may, it-is found, work to an advantage, inasmuch as it tendsto relieve excess internal pressures and prevents bulging of thecapacitor top during long continuous operation thereof at hightemperatures.

Referring now to Figure 3, there is shown an embodiment of the inventionwherein the electrolyte capacitor has a crimp type closure instead cithe screw type closure of Figure 1. The crimp closure structure is soconstructed that the casing may be of light weight and small size yet isstill capable of developing a seal which does not leak when cycledbetween the lowest and highest temperatures in the desired operatingrange.

In this embodiment a bimetal steel and silver drawn cup is used as thecontainer for the electrolyte and for the cathode of the capacitor ofthe cell. The cell top and anode assembly comprises a drawn tantalumsheet to which may be spot welded a tantalum pellet anode formed ofpressed and sintered metallic powder. As previously stated, a gasketmade of polytetra-iiuoroethylene polymer is used for the seal. Thisgasket seals the cell against electrolyte leakage and electricallyinsulates the anode and cathode assemblies.

The electrolytic capacitor, having a crimp type closure, is generallydesignated by reference numeral 60, and has a bimetal casing 6|fabricated of a steel layer 62 and a silver layer 63 with the silverlayer, adapted as formerly, to make contact with a sulphuric acidelectrolyte 86. Thus, silver layer 63 is adapted to act as an electrodeand becomes the cathode of the capacitor. The anode assembly, comprisesa sheet of tantalum metal e5 suitably joined to a pellet made frompressed and sintered metallic tantalum powder 56.

Case 6l, made of a bimetal sheet of steel and silver, is constructedwith a horizontal wall section 6'! and a vertical side wall section 58which provides a flat shoulder 'il around the top of the wafer shapedcapacitor. The outer wall section 63 is drawn down, as shown, to have aJ-shaped cross sectional configuration 69. The tantalum top of the cellis in the form of Va cup having tantalum anode pellet 66 properlycentered therein joined, as by inside welding, to tantalum member 65having arcuate sections 13, le, l5. A ridge 'iii is formed into theinside of the anode cup so as to be positioned directly opposite theshoulder 'il of the casing during assembly thereof.

Gasket i2, as stated, is made of polytetraiiuoroethylene polymer, and iscold drawn to slip over the anode pellet 66 and to ll the intersticesbetween the J-shaped section 69 of casing 6i and the arcuate sections'i3- l5 of the tantalum sheet 65. In assembly the cell electrolyte ofsulphuric acid is introduced into the case, the anode assembly ispressed on to the case and Vsealed' by crimping. The gasket 'i2 is thusconned under sufliciently high pressure to affect a seal able towithstand repeated cycling between the extremes of the desired operatingtemperature range.

In Figure 4, an embodiment Vof the invention is shown, wherein theelectrolytic capacitor is shown as being a modification of the inventiondescribed with respect to Figure 3, wherein means are afforded to allowtemperature compensation in the structure there disclosed. In addition,the cathode electrode, formed by a casing wall, may be depressed so astoafford substantially continuous contact therebetween and a desiredelectrolyte. As in Figure 3, electrolytic cell 8E has a casing wall 3imade from a bimetal strip, here shown as being constructed of athickness of steel 86 and silver 82.

In the construction of capacitor or cell 36, a drawn tantalum metal cup83 is provided, wherein tantalum powder 8d is pressed and sintered. Thepressed tantalum powder structure and the tantalummetal cup constitutethe anode assembly of the capacitor. The pressed tantalum anode consistsof pressed and sintered tantalum powder passing 250 mesh and retained on325 mesh. It has a pressed density of 135 g. per cubic inch and weighs9.4 grams. The drawn cup 83 and the sintered tantalum 3l! may be spotwelded to assure positive metallic contact therebetween. Cell isprovided with a top or cover 85, which as stated, maybe made of avsteeland silver-bimetal, or if .desired made by drawings steel ldisc and asilver disc placed together in a die. yIn any event, the cover-isconstructed so that-the silver becomes the inside surface. Further,cover 85 is adapted to act as the cathode.r of capacitor 80, and has itscenter, 8S depressed so asLto-pro- Vide substantially continuous contactbetween the cathode `and its contiguous.electrolyte; which maybe apredetermined concentrationiofsulphuric acid. Again, gasket 81, which asformerly, is fabricated of `a material not attacked .by strong sulphuric.acid at .approximately 200 C., and which. may be madeof.polytetraefiuoroethylene polymeris electrically .insulativelyinterposed in bracket-like fashion .between the silver. thickness t2 .ofthe cathode and .the anode ...assembly Gasketallmaybe punched from.sheet-stock and cold formed tov fit to cover 85.

Between.. anode cup andgasket'l there is interposed insulating washerandfsteel spring washer 89. Insulating washers 88 may be formed of asuitable insulating material, for example, mica, which will not flowunder pressure or a combination of heat and pressure and whichY willmaintain its electrical-insulating properties vover a wide `temperaturerange extending over approximately -60 C. to 200 C. insulating washerA88 isadapted to insulate anode cup. assembly 83 from spring washer 89and portions of the cathode circuit. Further, steel Vspringwasher 89 isconstructed so as to maintain pressurearound the seal when the capacitoris subjected tov alternate periods of high and low temperature operationwithin the operating range of the capacitor,

Tantalum cup 33 is constructed so that its top edge 943 is crimped overto form a support for thegasket and cover. It is to be noted, in theassembly of parts, that cover-85 is constructed with a slight taper sothat the top and gasket assembly may be easilyl slipped over the anodeassembly. and permit the escape of air-.as thetop assembly is sealed.insulating gasket or washer 83 and spring washer 39 are all positionedand the cover is crimped to seal the capacitor or cell. Further, theclosing die draws the cover with a slight taper toward the center andcrimps the edge thereof over the spring washer 4with sufricient pressureto compress the spring metal until it is nearly flat.

.The compensated crimped type ci closure, above described, provides acapacitor structure which is sealed sui'iiciently to .permit cyclingthroughout a temperature range substantially .of the range of 60 C. to2D()0 C. Because of vthe unique structural configuration of the `anodeassembly, there is a saving in the amount of tantalum required for thecell, with the construction thereof being such that the internalresistancepaths in the sintered tantalum structure are shortened so asto improve the resistance characteristics of the cell. Further, thenovel construction of the anode cup permits a more positive control of.electrolyte dispensing and allows for additional electrolyte capacitywhich aids in reducing theequivalent series resistance oi the cell.There is thus also provided a rugged anode assembly which is capable ofwithstanding, great mechanical shock Without breaking the bond betweenthe tantalum case and its associated sintered tantalum anodic structure..Moreoven Va novel seal is established which affords a substantiallygreater sealing area which assures great sealing effectiveness.

The electrolytic .capacitor ofthepresent inventionoperating over wideranges Yof temperature .and` pressure,: as herein above rdescribed ismerely illustrative .and Ynot-exhaustive infiscope and; since. manywidely different embodiments :of the .invention "may vbe .-:made.withoutl departing from Vthe .scope thereof, i it. is `intended .thatmatter icontained in the abovev fdeScriptiOnzand shown in .theaccompanyngdrawing.. shalllbe interposedias :illustrative and not .aVlimiting sense.

l`What is claimed-is:

l. An electrolytic capacitor adapted to operate over. a: wide'. range oftemperatures comprising :a container acting as a silver cathodetherefor, an anode placed` infsaidcontainer, VVsaid :anode beingAconstructed of asheet yof ,tantalum` and a pellet: connected thereto'and beingelectrically -insulatedfrom. said cathode, .said pellet' beingfabricated of pressed and sintered' metallic tantalumpowder,.an.electrolyte contiguous with saidcathode .and .said anode,means. for. maintaining ,the seal ofsaid vcapacitor at high temperatures`and pressures,..said. means vincluding agasket fabricated .ofamaterialinert tolsaid electrolyte; at high. temperatures v.contiguouslyplaced .between said sheetand said.cathode,.and'means `confining saidgasket '.materialunder .pressure to. maintain said capacitor seal.

' 2. An electrolytic lcapacitor ladapted; to .operate over a Widerange-of Atemperatures comprisingva silver casing therefor,- said'casingadapted toact as the cathode of saidcapacitonlsaid pellet-beingfabricated of .pressedand sinteredmetallic:tantalum powder, ananodeassemblyxcomprising ,a sheet or tantalum having` atantalumpelletconnectedz thereto contained `within saidcasing, .saidassembly being 'electrically insulated therefrom, asulphuric-acidelectrolyte contiguousfwith said anode `and vsaid casing,Vvseal means forIV sealing said capacitor -at high temperatures andpressures, said-sealing means fabricatedof -a=poly tetra-flu-oroethylenepolymer material ycontiguously placed between said tantalum sheet/andsaid cathode, and means for conning'said gasket underY pressure tomaintain the A'effective seal of said capacitor.

V8. An :electrolytic' capacitor` adapted to operate over a wide rangeof`temperatures'comprising'a casingtherefor, .said casing fabricated ofsilver and adapted to act as the cathode of said capacitor, an anodeassembly contained Within said casing and being electrically insulatedfrom .said cathode, said .assembly .comprising .a tantalum metal sheetanda pellet `fabricated of pressed and sintered metallic.powderconnected thereto, a sulphuricl acid electrolyte contiguousWithsaid anode and said-casing,v and means for maintaining y the seal of`said capacitorv at .high ytemperatures and pressures, saidmeansincludingfa gasket fabricated of a'material inertto said-velectrolyte at'high temperatures.

4. An electrolytic capacitoradapted Ato operate over a Wide range oftemperatures `.comprising a silver casing actingias .the 'cathodeth'ereoian anode assembly containedwithinsaid casing including. atantalumsheetand apelletr fabricated of pressed v`andsinteredmetallictantalumpowder, an electrolyte having arconcentrationofIabout 39% sulphuric acid placed nextsaid cathode-.and said anode, andmeans vfor maintainingtheseal of said capacitor at high temperaturesandpressures, "said means-including a gasket fabricated of apolytetra-uoroethylene 'polymer material contiguously placedl betweensaidsheetand said cathode.

5. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a casing fabricated of silver acting as acathode thereof, a tantalum anode comprising a sheet of tantalum towhich is connected a tantalum pellet contained within said casing, saidanode being electrically insulated therefrom by means of a gasketfabricated of polytetra-iluoroethylene polymer material, a sulphuricacid electrolyte contiguous with said casing and said anode, and sealingmeans for said capacitor maintaining the seal thereof at hightemperatures, said sealing means including means for confining a portionof said gasket material under pressure.

6. `An electrolytic capacitor adapted to operate overv a wide range oftemperatures comprising a silver container acting as a cathode thereof,an anode assembly including a sheet of tantalum connected to a pelletfabricated of pressed and sintered tantalum powder within saidcontainer, an electrolyte contiguous with said cathode and said anode,screw means for maintaining the seal of said capacitor at hightemperatures and pressures, said screw means including a base, a capscrewable thereon and a gasket fabricated of a material inert to saidelectrolyte at high temperatures.

v 7. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a casing having a wall fabricated of heavysilver material, ya tantalum anode placed within said casing, asulphuric acid electrolyte interposed between said casing and saidanode, sealing means for said capacitor to maintain the seal thereof athigh temperatures and pressures, said sealing means comprising a silverbase, a cap interlockably threadable thereupon and, a gasket fabricatedof -amaterial inert to said electrolyte interposed between said casingand said anode so as to electrically insulate the same and to aid in theeffective seal of said capacitor at high temperatures.

8. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a cathode constructed of a threaded silver baseand a cap threadably connected thereon, an anode fabricated of tantalumcontained within said cathode, an electrolyte interposed therebetween,an electrically vinsulated gasket interposed between said anode and saidcathode so as to insulate the same and to aid in the sealing of saidcapacitor at high temperatures.

9. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a container fabricated of a threaded silverbase, a Atantalum anode including a pellet fabricated of pressed andsintered metallic tantalum powder contained therewithin, an electrolytecontiguous with said anode and said container, a gasket fabricated of amaterial inert with respect to said electrolyte interposed between saidanode to electrically insulate the same, tab means connected to saidanode to act as a positive terminal therefor, a mica washer overlying aportion of said tab means connected to said anode and a screw cap meansplaced over said mica washer and screwably connected to said base ofsaid capacitor for maintaining the seal of the same at high temperatureranges.

10. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a container fabricated of a threaded silverbase, a, tantalum anode including a pellet fabricated of pressed andsintered metallic tantalum powder included therewithin, an electrolytecontiguous with said anode and said container, a gasket fabricated of amaterial inert with respect to said electrolyte interposed between saidanode and cathode to electrically insulate the same, tab means connectedto said anode to act as a positive terminal therefor, a micawasher'overlying a portion of said tab means connected to said anode,screw cap means placed over said mica Washer, and a washer made of steelspring overlying said tab means to maintain pressure thereupon.

11. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a silver container acting as a cathode therefor,a tantalum anode comprising a tantalum sheet and a pellet of sinteredand pressed tantalum powder connected thereto placed therewithin, saidanode being electrically insulated therefrom, an electrolyte contiguouswith said cathode and said anode, and crimp means for maintaining theseal of said capacitor at high temperatures and pressures, said crimpmeans having a J- shaped cross sectional configuration and including agasket made of polytetra-fluorcethylene polymer material for insulatingsaid container from said anode structure and to aid in maintaining aneffective seal for said capacitor at high temperatures.

l2. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a bimetal container fabricated of steel andsilver layers, said layer of silver adapted to act as the cathode ofsaid capacitor, an anode fabricated of tantalum metal placed in saidcontainer, said anode including a pellet fabricated of pressed andsintered metallic tantalum powder, an electrolyte interposed betweensaid cathode and said anode, and crimp means including a gasket made ofmaterial inert with respect to said electrolyte for electricallyinsulating said cathode from said anode and to aid in maintaining theseal of said capacitor at high temperatures and pressures.

13. An electrolytic capacitor comprising a casing fabricated of abimetal sheet of layers of steel and silver, a top of said casing madeof tantalum material, said top being in the form of a cup and includingan interconnected tantalum anode pellet and said top further having aridge formed therein, an electrolyte interposed between said tantalumpellet and said silver layer of said casing, and means interposedbetween said cup shaped tantalum top and said casing to electricallyinsulate the same and to aid in the formation of an effective seal forsaid cup, said material interposed between said top and said casingcomprising a material inert with respect to said electrolyte. V

14. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a. casing fabricated of a bimetal sheet havinglayers of steel and silver, said bimetal casing adapted to act as thecathode thereof, an electrolyte, a tantalum anode contained within saidcasing comprising a tantalum cup and a pressed tantalum powder structureconnected to said cup.

15. An electrolytic capacitor adapted to operate over a wide range oftemperatures comprising a casing fabricated of a bimetal sheet havinglayers of steel and silver, said bimetal casing adapted to act as thecathode thereof, a tantalum anode contained within said casingcomprising a, tantalum cup and a pressed tantalum powder structureconnected to said cup, an electrolyte interposed between said tantalumassembly and said silver layer of Vsaid casing, a steel spring aora-,soa

washer placed underneath said tantalum cup, a mica washer interposed:between said tantalum cup and said steel spring washer, and aninsulative material interposed between said anode cup and said steelwasher -to electrically insulate said tantalum cup from said silverlayer of said cathode and crimp means providing a seal with said bimetalcasing being further crimped about said material electrically insulatingsaid silver layer from said anode cup so as to maintain e'ective sealfor said cup.

16. An electrolytic capacitor adapted to operate over a Wide range oftemperatures comprising a bimetal casing fabricated of layers of steeland silver adapted to act as the cathode thereof, an anode comprising ananode cup and an anode pellet contained Within said casing, aelectrolyte placed within said anode cup, a depression formed Withinsaid bimetal casing to make contact with said electrolyte whereby saidsilver layer is in intimate association therewith, means insulating saidcasing from said anode cup, said means including a gasket fabricated ofpolytetraiiuoroethylene polymer material, and pressure 14 compensatingmeans placed underneath said anode cup comprising a mica. washer and asteel spring washer, said casing being crimped about said insulativematerial to form a seal for said capacitor.

GEORGE H. STINSON.

REFERENCES CITED The following references are of record in the tile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,753,912 Woodhull Apr. 8, 19301,914,114 Estes June 13, 1933 1,934,515 Tyzzer Nov. 7, 1933 2,037,848Brennan Apr. 21, 1936 2,060,866 Hetenyi Nov. 17, 1936 2,104,019 BrennanJan. 4, 1938 2,162,385 Langguth June 13, 1939 2,299,228 Gray Oct. 20,1942 2,357,554 Sears Sept. 5, 1944 2,359,970 Clark Oct. 10, 19442,368,688 Taylor Feb. 6, 1945

1. AN ELECTROLYTIC CAPACITOR ADAPTED TO OPERATE OVER A WIDE RANGE OFTEMPERATURES COMPRISING A CONTAINER ACTING AS A SILVER CATHODE THEREFOR,AN ANODE PLACED IN SAID CONTAINER, SAID ANODE BEING CONSTRUCTED OF ASHEET OF TANTALUM AND A PELLET CONNECTED THERETO AND BEING ELECTRICALLYINSULATED FROM SAID CATHODE, SAID PELLET BEING FABRICATED OF PRESSED ANDSINTERED METALLIC TANTALUM POWDER, AN ELECTROLYTE CONTIGUOUS WITH SAIDCATHODE AND SAID ANODE, MEANS FOR MAINTAINING THE SEAL OF SAID CAPACITORAT HIGH TEMPERATURES AND PRESURES, SAID MEANS INCLUDING A GASKETFABRICATED OF A MATERIAL INERT TO SAID ELECTROLYTE AT HIGH TEMPERATURESCONTIGUOUSLY PLACED BETWEEN SAID SHEET AND SAID CATHODE, AND MEANSCONFINING SAID GASKET MATERIAL UNDER PRESSURE TO MAINTAIN SAID CAPACITORSEAL.